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Cornell Department of Astronomy and Space Sciences Colloquium

Thursday, December 10, 2020 at 4:00pm to 5:00pm

Virtual Event

'Imaging and Beyond: Towards Event Horizon Telescope-Scale Physics from "Observing" JAB Simulations"


Recent radio observations of emission from infalling and outflowing plasma in the vicinity of supermassive black holes are linked to simple phenomenological models via general relativistic magnetohydrodynamic simulations using a methodology called "Observing" Jet (or outflow)/Accretion flow/Black hole (JAB) Simulations. For Sagittarius A* in our Galactic Center, movies simulating hourly timescales show that these models can be classified into at least four types: 1.) thin, asymmetric photon ring with best fit spectrum; 2.) coronal boundary layer with thin photon ring and steep spectrum; 3.) thick photon ring with flat spectrum; and 4.) extended outflow with flat spectrum. For M87, a self-similar, stationary, axisymmetric model based on a force-free flow in a HARM jet simulation is used to generate Stokes maps at Global mm-VLBI Array (86 GHz) and Event Horizon Telescope (230 GHz) scales. This model varies plasma content from ionic (e-p) to pair (e-e+). Emission at the observed frequency is assumed to be synchrotron radiation from electrons and positrons, whose pressure is set to relate to the local magnetic pressure through parametric prescriptions.  Polarization maps are found to be sensitive to the positron effects of decreasing intrinsic circular polarization and increased Faraday conversion.



Dial-In Information

The colloquia are held every Thursday afternoon 4-5 pm. The public is welcome. To view via Zoom, please contact Monica Carpenter ( or Jason Jennings ( for the link.

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Contact Name

Monica Carpenter

Contact Phone



Richard Anantua

Speaker Affiliation

Harvard-Smithsonian Center for Astrophysics

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